1. ¹Department of Molecular Biology, Institute of Nanosensor and Biotechnology, Dankook University, Seoul 140-714, Korea
2. ²Research Institute and Hospital, National Cancer Center, Koyang 411-764, Korea
3. ³Genoprot Inc., Seoul 153-803, Korea
4. ⁴National Institute of Health, Seoul 122-701, Korea
5. ⁵Department of Pathology, Dong-A University College of Medicine, Busan 602-103, Korea

Correspondence: Seong-Wook Lee, Department of Molecular Biology, Dankook University, San8, Hannam-Dong, Yongsan-Gu, Seoul 140-714, Korea. Fax: +82 2 798 4733. E-mail: SWL0208@dankook.ac.kr

^*These authors contributed equally to this article.

Received 31 December 2004; Revised 8 June 2005; Accepted 19 June 2005.

Abstract

In this study, we describe a novel approach to human cancer therapy that is based upon trans-splicing ribozyme-mediated replacement of cancer-specific RNAs with new transcripts that exert therapeutic activities. We have developed a specific ribozyme that can reprogram human telomerase reverse transcriptase (hTERT) RNA to induce transgene activity selectively in cancer cells that express the RNA. The ribozyme-mediated triggering of the transgene expression was accomplished via a high-fidelity trans-splicing reaction with the targeted residue in the hTERT-expressing cells. The ribozyme also induced cytotoxic activity in various hTERT-expressing cancer cells, hence selectively retarding the growth of those cells. Efficient and specific cell regression was also detected with ganciclovir (GCV) treatment only in hTERT-positive cancer cells, which were established to express stably the specific ribozyme that contains the herpes simplex virus thymidine kinase (HSV-tk) gene. Tissue-specific expression of the ribozyme could further augment the target specificity of the ribozyme. Importantly, we observed efficient regression of tumors with GCV treatment in mice that had been inoculated subcutaneously with hTERT-positive cancer cells that stably expressed the specific ribozyme that contains HSV-tk. These results suggest that the hTERT RNA-targeting trans-splicing ribozyme could be a powerful agent for tumor-targeted specific gene therapy.